1. Field of the Invention
The invention relates to an optical recording system, more particularly to a method and device for correcting optical path deviation of an optical pickup in an optical recording system so as to improve the recording and playback quality while keeping manufacturing costs low.
2. Description of the Related Art
Referring to FIG. 1, a conventional optical recording system 1 is shown to include a spindle motor 10 for driving rotation of an optical recording medium 2, a first servo controller 11 for controlling operation of the spindle motor 10, an optical pickup 12 for recording data onto and reading data from the optical recording medium 2, a sled motor 13 for driving radial movement of the optical pickup 12 relative to the optical recording medium 2, a second servo controller 14 for controlling operation of the sled motor 13 and adjustment of an objective lens 121 of the optical pickup 12, a pre-amplifier 15 for receiving the output of a photo detector 122 of the optical pickup 12, a central processing unit (CPU) 16, a digital signal processor (DSP) 17 controlled by the CPU 16 for processing signals from the pre-amplifier 15 and for controlling operations of the first and second servo controllers 11, 14, and a decoder 18 for decoding data read from the optical recording medium 2.
To meet consumer demands for reasonable prices, manufacturers of optical recording systems have to continuously strive to find ways to lower manufacturing costs. As a result, the precision requirements for fabricating and installing the optical pickup 12, which is a critical component of the optical recording system 1, are typically sacrificed. Moreover, proper biasing of an internal circuit of the second servo controller 14, which is responsible for focusing and track-locking control of the optical pickup 12, is also sacrificed such that an output signal of the second servo controller 14 may be non-zero when an input thereto is zero. In addition, warping of the optical recording medium 2 is likely to occur during recording and/or playback due to errors in the manufacturing process and non-ideal operating conditions.
The aforesaid factors can result in optical path deviation of the optical pickup 12, i.e., with reference to FIG. 2, when the optical pickup 12 is used to record data onto or read data from an optical recording medium, the light beam 20 reflected from the optical recording medium deviates from and does not coincide with a central portion of the photo detector 122 (which includes a 2×2 array of light-sensing regions (A), (B), (C), (D)). Hence, when the DSP 17 controls the second servo controller 14, the servo control signals generated by the second servo controller 14 contain undesired bias components, which degrade the recording and playback quality.
Therefore, there is always a need in the industry to find ways to improve the recording and playback quality while keeping manufacturing costs low.